Combustion turbines comprise a casing for housing a compressor section, combustor section and turbine section. Each one of these sections comprise an inlet end and an outlet end. A combustor transition member is mechanically coupled between the combustor section outlet end and the turbine section inlet end to direct a working gas from the combustor section into the turbine section. Conventional combustor transition members may be of the solid wall type or interior cooling channel wall type (see FIG. 1). In either design, the combustor transition member is formed from a plurality of metal panels.
The working gas is produced by combusting an air/fuel mixture. A supply of compressed air, originating from the compressor section, is mixed with a fuel supply to create a combustible air/fuel mixture. The air/fuel mixture is combusted in the combustor to produce the high temperature and high pressure working gas. The working gas is ejected into the combustor transition member to change the working gas flow exiting the combustor from a generally cylindrical flow to an generally annular flow which is, in turn, directed into the first stage of the turbine section.
As those skilled in the art are aware, the maximum power output of a gas turbine is achieved by heating the gas flowing through the combustion section to as high a temperature as is feasible. The hot working gas, however, may produce combustor section and turbine section component metal temperatures that exceed the maximum operating rating of the alloys from which the combustor section and turbine section are made and, in turn, induce premature stress and cracking along various turbomachinary components, such as a combustor transition member.
Several prior art apparatus have been developed to cool combustor transition members. Some of these apparatus include impingement plates, baffles, and cooling sleeves spaced about the combustor transition member outer surface. These apparatus, however, have several drawbacks.
One drawback with these prior art cooling apparatus is that each type of cooling apparatus can only be employed with a specific transition member. If one owns combustion turbines that require various types of transition members, then an inventory of various types of cooling apparatus are required for maintenance purposes. It would, therefore, be desirable to provide a cooling apparatus that can be employed with more than one type of transition member.
Other conventional methods have been developed to overcome the need for separate apparatus for cooling a transition. FIG. 1, which shows one of these methods, is a transition member 20 having a sidewall 22 that defines an interior working gas flow channel 24. The interior working gas flow channel has an inlet end 26 and exit end 28. The sidewall 22 comprises a plurality of interior cooling flow channels 30, cooling air entrance holes 32 and cooling air exit holes 35. The transition member 20 is cooled by a cooling fluid that enters the cooling air entrance holes 32, travels through the interior cooling flow channels 30, exits past the exit holes 35, and, in turn, enters into the working gas flow channel 24.
The transition member 20 is manufactured from a plurality of panels 34 that define the interior cooling flow channels 30 and cooling air exit holes 35, as shown in FIG. 2. The panels 34 are made from a first metal plate 36 and second metal plate 38. The interior cooling flow channels 30 are formed by attaching the first metal plate 36 and second metal plate 38 together. The first metal plate 36 is formed with a plurality of grooves 40 that extend along a relative longitudinal direction for substantially the entire length of the first plate 36. The exit holes 35 are formed in the first plate 36 in fluid communication with at least one groove 40. The second plate 38 is formed with the cooling flow entrance holes 32 which are in fluid communication with the grooves 40 After attaching the first 36 and second panels 38 together, a plurality of cooling panels are formed into the desired shape to form a particular transition member. Transition members 20 made from these panels 34, however, have several drawbacks.
One drawback of employing this type of transition member 20 is that they commonly fail at a relatively small area along the interior cooling flow channel 30. The area that fails cannot be repaired or replaced and, therefore, the entire transition member 20 must be replaced. The replacement of an entire transition member 20 is relatively costly. It would, therefore, be desirable to provide a transition member that allows for the replacement of less than the entire transition member after the transition member has suffered less than an entire failure.